This invention relates to leak detection methods and apparatus for diagnostic purposes, and more particularly relates to methods and means for locating leaks in any closed vacuum system in the internal combustion engine.
It is well known in the prior art that an automobile cooling system is intended to be a closed system which enables heat transfer from an operating engine to its water, circulated by a water pump to the radiator which transfers heat from the water to the atmosphere. A leak in the cooling system, typically occurring in a hose, in a clamped connection, or in the walls of the radiator, significantly reduces the cooling efficiency thereof, and may cause overheating of and possible damage to the engine.
It is also well known in the prior art that the internal combustion engine commonly used in automobiles and trucks, contains several vacuum induction systems involving carburetion, fuel injection, power braking, air conditioning, emission control, etc. If a leak occurs in one or more of these closed systems, the operating efficiency of the internal combustion engine is clearly reduced. Indeed, the evasion of air into such vacuum induction systems is a common problem. Vacuum leaks are frequently found even on new cars.
Vacuum leaks in the internal combustion engine, characterized by multiple layers of gaskets, hoses, interconnections, etc., are difficult to find. It frequently necessitates dismantling a particular system and examining individual hoses and their concomitant connections. As an example, in the trucking industry the typical large diameter hoses are disassembled and individually examined for cracks and minute holes with a flashlight or even a light bulb.
Interestingly, many vehicles with computerized control of the internal combustion operation, typically attempt to compensate for such vacuum leaks and the like, instead of diagnosing and suggesting repairs for such leaks. There have been many attempts in the prior art to provide leak detection means and methods for specific portions of a closed system in the internal combustion engine, but there have been few focusing on leak detection for an entire system.
For example, Carney, in U.S. Pat. No. 4,494,402, discloses a device and method for measuring the pressure integrity of a cooling system and the existence of coolant leaks in an automobile. The Carney device attempts to overcome the limitation of the prior art whereby at least two tests must be performed to ascertain the integrity of the entire cooling system, i.e., testing the radiator cap and the remainder of the cooling system separately. More particularly, by configuring a radiator cap to sealably receive a conduit with pressurized air passing therethrough, Carney enables the fluid tightness of the entire cooling system to be simultaneously determined. It is clear to those skilled in the art that the Carney method and means is not applicable to leak detection in vacuum systems.
In U.S. Pat. No. 3,786,671, Caron teaches a vehicle vacuum chamber leak testing device which provides two sleeves having hoses for interconnection with the vacuum intake manifold and another port of entry, of the particular closed system being tested. A spring-diaphragm combination is integrated therewith whereby a leak is indicated when the spring is forced to engage the diaphragm because air has replaced the vacuum.
Similarly, Eason, in U.S. Pat. No. 4,047,423, discloses a leak detector for selectively determining leaks in particular passageways in an automobile engine. In particular, this apparatus provides angular coupling means for engaging opposite ends of the passageway, and then applying air pressure thereto. The behavior thereof under pressure is observed on a pressure gauge mounted on the Eason device. In addition to subjecting such passageway to high pressure, the Eason method can only test a limited portion of a closed system in order to properly locate the source of leaks. U.S. Pat. No. 4,235,100, discloses another version of such a pressure testing device which a cooling system is forced pressurized, and then examined for the existence of pressure drops or fluid leaks.
While, as hereinbefore exemplified, practitioners in the art have attempted to improve the means for detecting significant leaks in the closed systems inherent in the internal combustion engine, there has been less effort expended to detect minor leaks therein. But, with the demands placed upon the performance of such engines necessitating lower compression ratios, using leaner fuel mixtures and to comply with emission control standards of the United States Environmental Protection Agency, even small or minute leaks, particularly vacuum leaks, are apt to be detrimental to the performance thereof.
U.S. Pat. No. 4,667,507, granted to Eriksson, illustrates an attempt to improve the detection art relative to small leakages caused by correspondingly small defects and the like in the cylinder head gasket and the engine block. The Eriksson device provides a means and method for detecting compression leaks during the operation of an internal combustion engine, but fails to detect vacuum leaks therein.
It is well known in the art that smoke may be used to detect the existence of leaks, but smoke detection means have not hitherto been applied to leak detection in internal combustion engines in automobiles and the like. For example, U.S. Pat. Nos. 4,198,856; 4,330,428; 4,694,695; and 3,395,514; illustrate concept of using smoke under pressure to determine leakage. Similarly, U.S. Pat. No. 3,444,721, teaches using a trace gas under pressure to determine leaks along a pipeline. The novel application of such smoke-detection art to test for vacuum leaks in an internal combustion engine, would provide a heretofore unknown technique for quickly, effectively and reliably assessing the integrity of any vacuum system in the automobile engine and the like. Indeed, by providing a cost-effective means and method for properly and regularly testing an engine for vacuum leaks, not only can the longevity and operating efficiency of the engine, per se, be improved, but also the quality of the environment.
Accordingly, these limitations and disadvantages of the prior art are overcome with the present invention, and improved means and techniques are provided which are useful for using smoke for detecting leaks in closed systems in automobile engines and the like.